Weak Magnetic Field Sensors Based On Magnetoelectric Effect And High Performance Relaxor Ferroelectric Single Crystal

The magnetoelectric?ME?effect is defined as induced electric polarization under an applied magnetic field,or conversely as induced magnetization under an applied electric field in a magntoelectric material,which has been used in information storage,biomedicine,energy conversion,etc.In this dissertation,the passive magnetic sensor based on heterostructure ME composite has been discussed.The working principle of the ME magnetic sensor is the conversion of magnetic field to voltage by the ME composite integrated with specific amplifier circuit.Nowadays,the ME magnetic sensor made by high performance relaxor single crystals already has the ability to compete with traditional magnetic field sensors of fluxgate and coil in some indicators,such as sensitivity,bandwidth,power consumption,volume,as well as cost.And the ME magnetic sensor has already been used in the applications of underwater electromagnetic field inspection,geological prospecting,electromagnetic location.By establishing the model of the noise equivalent magnetic induction?NEB?,fabricating high performance ME materials,designing extremely low noise amplifier circuit,improving sensor packaging,the sensitivity of ME sensor for low-frequency version has been achieved as 3.2 pT/Hz^1/2@1 Hz,for high-frequency version has been achieved as 9.1 fT/Hz^1/2@17.24 kHz,and for LCR version has been achieved as 0.26pT/Hz^1/2@25.2 kHz.The main works in this dissertation are as follows:Four kinds of L-L mode ME composite based on Metglas alloy and PMNT single crystal,MLT mode ME composite based on Metglas alloy and Mn-PMNT single crystal,L-W mode ME composite based on Terfenol-D alloy and PMNT single crystal,L-T mode ME composite based on Metglas alloy and PMNT single crystal have been designed and fabricated.The ME coefficients,dielectric loss,NEB,resonance characteristics of these ME material has been measured.We also use models combined with finite element simulation to analyze the geometry effect in the ME material.Based on the MLT mode ME composite and amplifier circuit,we fabricate low-frequency and high-frequency version ME magnetic sensors,respectively.And the influence of the parameters of ME composite and amplifier circuit has been discussed.Based on the LCR mode ME composite,we fabricate LCR version ME sensors,which can break through the limitation of size-dependence of the resonance frequency.Using equivalent circuit model,the response and noise characters of the LCR version ME sensors have been analyzed.We explore the applications of the ME magnetic sensor in underwater electromagnetic field inspection and endoscope electromagnetic location systems.For the electromagnetic field inspection,the triaxial ME magnetic sensor and towed ME magnetic sensor have been made by MLT mode ME composite.The relations between velocity,distance and magnetic moment with the output signals have been measured.For the location systems,the LCR version ME sensors with lower NEB and high resonance Q value has been compared with coil sensors in the frequency range of 1 kHz to 30 kHz.